There exist in the market bags containing grains of maize specially adapted for making popcorn in a microwave oven of the household type, simply by placing the bag in the microwave oven for a certain length of time. The bag inflates as the grains of maize expand to form the popcorn.
Known in the art commercially for the supply of recently made bags of popcorn is a dispensing machine with a simple system of gravity feed for the bags to take them into a microwave oven; this oven is provided with a loading door in its upper part and a finished-product expulsion door or hatch in its lower part.
These known machines nevertheless present a number of major disadvantages. On the one hand, the need to have a microwave oven of special construction increases the cost of the machine unacceptably; and on the other hand, the feed system for this dispensing machine is not entirely reliable, and the bags often become stuck or do not reach the oven correctly.
More specifically, on some machines the feed is implemented by means of vertical channels in which the products are stored in the form of a pile; the last of the products from the pile is driven by a piston and falls by gravity towards the oven. Such systems, similar to those used for cigarette machines and the like, are not suitable for products with irregular packaging, such a popcorn bags, for the bag is often poorly positioned in relation to the piston and blockages occur or the pistons fails to push any of the product; moreover, the bags can be oily and not slide correctly along the ramps which take them to the oven, so that these machines end up presenting undesirable operating defects.
The right cooking time for the popcorn depends on several parameters, such as the type and size of maize grain, humidity, ambient and product temperatures, wear of the magnetron, and others. On the known machine described, cooking control is limited to a timer which switches the oven off after a preset time, so that cooking time cannot be varied; this is a major limitation, for it means that some grains do not burst, some bags may even catch fire, etc.
Another disadvantage of this machine is that it permits the supply of only one specific product, while it would be desirable for one machine to be able to supply several different articles, at the choice of the customer.